N4.2 Convergence

welcome to unit four Oceanic Oceanic or oceanic continental convergence um so we're going to be talking about what is Convergence and what causes it why do I have plates that run into each other why don't so uh so right now what I want you to do I want you to after I read the directions I want you to pause and pause the video and stop and think about it so the question is which two plates a B and C are converging so you're going to pick two letters between a b and c and then um

at Point X or Y is the con at what point x or y is the convergence happening and then what is the athenos spere doing at that point so once again stop and think which two plates are converging where is it converging and what is the athenos here doing at that point all right so um so this model is the green plates uh the green boxes represent represent oceanic plates or or or any plate to be fair uh so oceanic continental does not matter the green box are are plates and then these red arrows represents

athenos spere convection okay so I have three convection currents in the athenos spere now the biggest thing to answering this question is realizing that the bottom what is happening down here does not have any effect on what is happening on top so what's happening at the bottom of the convection currents has no effect on what's happening at the top since these lithospheric plates are literally floating in the athenos spere it's only where they're floating that makes a difference so uh so the very top where they're floating if that's moving the plates will move in the

same direction side note on this you will see a question like this on your test so which two plates are converging the two plates that are converging are plates B and C we see that this a this convection current is pushing B to the right and this convection current is pushing B or C to the left into each other side note if you said A and B A is moving to the left and B is moving to the right so those would actually be diverging away from each other something we'll talk about so the convergence

is happening at point Y so I would expect a convergent boundary that plate why because B is moving to the right and C is moving towards the left into each other and what is the athenos spere convection current doing it is it's coming together and then sinking or what's called um down Welling at that point so upwelling down willing so at B and C the the athenos spere is down willing that cool less dense or that cool now denser athenos spere is sinking back down okay so the BNC happens where that now cold athenos fere

is sinking back down basically down to be reheated at some point so uh Oceanic Oceanic or oceanic continental conversions occurs when plates run into each other that literally means what convergence means converge come together um those are the big things this occurs over the downwelling athenos spere um the way I like to imagine this um my children uh take baths with lots of toys they're right now when I'm making this video they are both five and one's turning uh three shortly they take baths with lots and lots of toys okay so I have all these

toys floating on the surface of the water I open the drain the water starts flowing to the drain and then down the drain and what ends up happening is all those toys move together towards the drain because the the drain the water is going down out of the tub and so all the toys start to converge on that drain because they're all floating and all the water is moving towards that drain something similar happening too where the athenos is downwelling the athenos spere is moving towards that point and then going down so everything floating on

the athenos spere at those points will be pulled or pushed however you want to think about it to that Central Point okay in general um when you have two plates of lith when you have two plates of lith when you have two different two lithospheric plates colliding the denser one is going to be subducted so in the case of a continental Oceanic the oceanic crust is denser the continental crust so if I have a piece of continental crust meaning a piece of oceanic the oceanic one will subduct underneath or go down under if I have

two piece of oceanic crust the older colder and denser lithosphere will go down okay